I have a B81SX with single acting service brake chambers on the tandems. The truck utilized a hand brake that engaged a brake drum on the drive shaft for parking. From the attached pictures does anybody know if there is a parking brake chamber type that is a direct bolt on? The current setup only utilizes one bolt to secure the chamber to the axle housings. All the spring brake chambers I have seen have two bolts. Has anybody ever done this change to older trucks that were not originally equipped with spring brakes? I realize there is air line plumbing involved and a valve needs added in the cab, however I believe that to be the easy part of this job. My concern is with being able to mount a spring brake chamber to the axle housings. This truck is 90% restored and is used only for show, however, the lack of a good functioning parking brake is somewhat of a liability in my eyes. Let me know if you have any ideas. Thanks in advance.